[ENH] Drawables: revenge of the lint

[rksh]

A bunch of little visual linting checks. Grouped together because none of these reall bear much review.

• xhdpi drawable asset directory was missing a lot of versions
• an old, low-res grayscale planet icon was doing mixed/triple duty at points in the UI
• android 24-29 had a mismatched icon in notification bar
• DP sizes in icons were inconsistent across DPI folders
• removing a lint warning in our port of the map bubble UI (because we learned it from Google)
• an errant dimens entry

[bobzilladev]

i assume it looks good!